Operation for 3D beam forming in a wireless communication system

ABSTRACT

Here, operation for 3D beam forming is disclosed. UE, receiving reference signals from one or more base stations (eNBs), may report feedback information comprising precoding matrix information to the one or more eNBs. The precoding matrix information indicates a first type precoding matrix for a horizontal direction and a second type precoding matrix for a vertical direction. eNBs may transmit signals, which are precoded based on a third type precoding matrix for beam forming both on the horizontal direction and the vertical direction.

CROSS REFERENCE

This application is a continuation of U.S. patent application Ser. No.16/005,201, filed on Jun. 11, 2018, which is a continuation of U.S.patent application Ser. No. 14/552,918, filed on Nov. 25, 2014, nowissued as U.S. Pat. No. 10,009,075, which claims the benefit of the U.S.Provisional Application No. 61/909,375, filed on Nov. 27, 2013, all ofwhich are incorporated by reference in their entirety herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to methods for an operation for 3D beam forming andapparatuses therefor.

Discussion of the Related Art

As an example of a wireless communication system to which the presentinvention is applicable, a 3rd generation partnership project (3GPP)long term evolution (LTE) communication system will be schematicallydescribed.

FIG. 1 is a schematic diagram of E-UMTS network structure as an exampleof a wireless communication system.

E-UMTS (evolved universal mobile telecommunications system) is thesystem evolved from a conventional UMTS (universal mobiletelecommunications system) and its basic standardization is progressingby 3GPP. Generally, E-UMTS can be called LTE (long term evolution)system. For the details of the technical specifications of UMTS andE-UMTS, Release 7 and Release 8 of ‘3rd Generation Partnership Project:Technical Specification Group Radio Access Network’ can be referred to.

Referring to FIG. 1, E-UMTS consists of a user equipment (UE) 120, basestations (eNode B: eNB) 110 a and 110 b and an access gateway (AG)provided to an end terminal of a network (E-UTRAN) to be connected to anexternal network. The base station is able to simultaneously transmitmulti-data stream for a broadcast service, a multicast service and/or aunicast service.

At least one or more cells exist in one base station. The cell is set toone of bandwidths including 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, 20MHz and the like and then provides an uplink or downlink transmissionservice to a plurality of user equipments. Different cells can be set toprovide different bandwidths, respectively. A base station controls datatransmissions and receptions for a plurality of user equipments. A basestation sends downlink scheduling information on downlink (DL) data toinform a corresponding user equipment of time/frequency region fortransmitting data to the corresponding user equipment, coding, datasize, HARQ (hybrid automatic repeat and request) relevant informationand the like. And, the base station sends uplink scheduling informationon uplink (UL) data to a corresponding user equipment to inform thecorresponding user equipment of time/frequency region available for thecorresponding user equipment, coding, data size, HARQ relevantinformation and the like. An interface for a user traffic transmissionor a control traffic transmission is usable between base stations. Acore network (CN) can consist of an AG, a network node for userregistration of a user equipment and the like. The AG manages mobilityof the user equipment by a unit of TA (tracking area) including aplurality of cells.

The wireless communication technology has been developed up to LTE basedon WCDMA but the demands and expectations of users and service providersare continuously rising. Since other radio access technologies keepbeing developed, new technological evolution is requested to becomecompetitive in the future. For this, enhancement in MIMO technology isdemanded for better communication.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to methods for operatingfor 3D beam forming and apparatuses therefor that substantially obviatesone or more problems due to limitations and disadvantages of the relatedart.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for a user equipment (UE) to operate in a wireless communicationsystem is provided. The method comprises: receiving reference signalsfrom one or more base stations (eNBs); reporting feedback informationcomprising precoding matrix information to the one or more eNBs, whereinthe precoding matrix information indicates a first type precoding matrixfor a horizontal direction and a second type precoding matrix for avertical direction; and receiving signals from the eNBs, wherein thesignals are precoded based on a third type precoding matrix for beamforming both on the horizontal direction and the vertical direction.

In another aspect of the present invention, a user equipment foroperating in a wireless communication system is provided. The UEcomprises: a transceiver adapted to transmit or receive signals over theair; a microprocessor electrically connected to the transceiver andadapted to control the transceiver to: receive reference signals fromone or more base stations (eNBs); report feedback information comprisingprecoding matrix information to the one or more eNBs, wherein theprecoding matrix information indicates a first type precoding matrix fora horizontal direction and a second type precoding matrix for a verticaldirection; and receive signals from the eNBs, wherein the signals areprecoded based on a third type precoding matrix for beam forming both onthe horizontal direction and the vertical direction.

The third type precoding matrix may be selected by considering acombination of the first type precoding matrix and the second typeprecoding matrix corresponding to the precoding matrix information.

The third type precoding matrix may correspond to a Kronecker product ofthe first type precoding matrix and the second type precoding matrixcorresponding to the precoding matrix information.

The first type precoding matrix may be selected from a first typecodebook comprising Rank 1 to Rank M precoding matrixes, the Mcorresponding to a number of transmission antennas, and the second typeprecoding matrix may be selected from a second type codebook comprisingRank 1 precoding matrixes.

The precoding matrix information may comprise a first index forindicating the first type precoding matrix and a second index forindicating the second type precoding matrix. In this case, the reportingfeedback information may comprise: reporting the first index with afirst period; and reporting the second index with a second period,wherein the second period is longer than the first period.

The second type precoding matrix selected based on the second index isdifferently selected based on the first index.

The first type codebook may comprise precoding matrixes for beam formingin the horizontal direction with equal horizontal angle distribution,and the second type codebook may comprise precoding matrixes for beamforming in the vertical direction with different vertical angledistribution.

The second codebook may comprise more precoding matrixes for beamforming with vertical angle for 0°˜45° than precoding matrixes for beamforming with vertical angle for 45°˜90° and 0°˜−90°.

The second codebook may comprise more precoding matrixes for beamforming with vertical angle for 0°˜45° than precoding matrixes for beamforming with vertical angle for −45°˜−90° and 0°˜90°.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a schematic diagram of E-UMTS network structure as an exampleof a wireless communication system.

FIG. 2 is a diagram for explaining physical channels used by 3GPP systemand a general signal transmitting method using the same.

FIG. 3 is a diagram for a configuration of a general multi-antenna(MIMO) communication system.

FIGS. 4 a, b and c are diagrams describing an antenna tilting system.

FIGS. 5 a and b are diagrams illustrating one example of comparing anexisting antenna system and an active antenna system to each other.

FIG. 6 shows a general AAS Radio Architecture for implementing thepresent invention.

FIGS. 7 and 8 show examples of 2D Array structure.

FIG. 9 is a diagram for defining elevation angle and horizontal angle.

FIG. 10 shows an example of deployment of 2D array in 3D space.

FIGS. 11-14 show application of 3D beam forming according to the presentinvention.

FIG. 15 shows a concept of feedback the precoding matrix information inaccordance with the present embodiment of the invention.

FIG. 16 is a block diagram of a communication apparatus according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The configuration, operation and other features of the present inventionwill be understood by the embodiments of the present invention describedwith reference to the accompanying drawings. The following embodimentsare examples of applying the technical features of the present inventionto a 3rd generation partnership project (3GPP) system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition.

FIG. 2 is a diagram for explaining physical channels used by 3GPP systemand a general signal transmitting method using the same.

Referring to FIG. 2, if a power of a user equipment is turned on or theuser equipment enters a new cell, the user equipment performs an initialcell search for matching synchronization with a base station and thelike [S301]. For this, the user equipment receives a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the base station, matches synchronization with the basestation and then obtains information such as a cell ID and the like.Subsequently, the user equipment receives a physical broadcast channelfrom the base station and is then able to obtain intra-cell broadcastinformation. Meanwhile, the user equipment receives a downlink referencesignal (DL RS) in the initial cell searching step and is then able tocheck a downlink channel status.

Having completed the initial cell search, the user equipment receives aphysical downlink control channel (PDCCH) and a physical downlink sharedcontrol channel (PDSCH) according to information carried on the physicaldownlink control channel (PDCCH) and is then able to obtain systeminformation in further detail [S302].

Meanwhile, if the user equipment initially accesses the base station orfails to have a radio resource for signal transmission, the userequipment is able to perform a random access procedure (RACH) on thebase station [S303 to S306]. For this, the user equipment transmits aspecific sequence as a preamble via a physical random access channel(PRACH) [S303, S305] and is then able to receive a response message viaPDCCH and a corresponding PDSCH in response to the preamble [S304,S306]. In case of contention based RACH, it is able to perform acontention resolution procedure in addition.

Having performed the above mentioned procedures, the user equipment isable to perform PDCCH/PDSCH reception [S307] and PUSCH/PUCCH (physicaluplink shared channel/physical uplink control channel) transmission[S308] as a general uplink/downlink signal transmission procedure. Inparticular, the user equipment receives a downlink control information(DCI) via PDCCH. In this case, the DCI includes such control informationas resource allocation information on a user equipment and can differ informat in accordance with the purpose of its use.

Meanwhile, control information transmitted/received in uplink/downlinkto/from the base station by the user equipment includes ACK/NACK signal,CQI (channel quality indicator), PMI (precoding matrix index), RI (rankindicator) and the like. In case of the 3GPP LTE system, the userequipment is able to transmit the above mentioned control informationsuch as CQI, PMI, RI and the like via PUSCH and/or PUCCH.

FIG. 3 is a diagram for a configuration of a general multi-antenna(MIMO) communication system.

N_(T) transmitting antennas are provided to a transmitting stage, whileN_(R) receiving antennas are provided to a receiving stage. In case thateach of the transmitting and receiving stages uses a plurality ofantennas, theoretical channel transmission capacity is increased morethan that of a case that either the transmitting stage or the receivingstage uses a plurality of antennas. The increase of the channeltransmission capacity is in proportion to the number of antennas. Hence,a transmission rate is enhanced and frequency efficiency can be raised.Assuming that a maximum transmission rate in case of using a singleantenna is set to R₀, the transmission rate in case of using multipleantennas may be theoretically raised by a result from multiplying themaximum transmission rate R₀ by a rate increasing rate R_(i), as shownin Equation 1. In this case, R_(i) is a smaller one of N_(T) and N_(R).R _(i)=min(N _(T) ,N _(R))  [Equation 1]

For instance, in an MIMO communication system, which uses 4 transmittingantennas and 4 receiving antennas, it may be able to obtain atransmission rate 4 times higher than that of a single antenna system.After this theoretical capacity increase of the MIMO system has beenproved in the middle of 90's, many ongoing efforts are made to varioustechniques to substantially improve a data transmission rate. And, thesetechniques are already adopted in part as standards for the 3G mobilecommunications and various wireless communications such as a nextgeneration wireless LAN and the like.

The trends for the MIMO relevant studies are explained as follows. Firstof all, many ongoing efforts are made in various aspects to develop andresearch information theory study relevant to MIMO communicationcapacity calculations and the like in various channel configurations andmultiple access environments, radio channel measurement and modelderivation study for MIMO systems, spatiotemporal signal processingtechnique study for transmission reliability enhancement andtransmission rate improvement and the like.

In order to explain a communicating method in an MIMO system in detail,mathematical modeling can be represented as follows. Referring to FIG.3, assume that N_(T) transmitting antennas and N_(R) receiving antennasexist. First of all, regarding a transmission signal, if there are N_(T)transmitting antennas, N_(T) maximum transmittable informations exist.Hence, the transmission information may be represented by the vectorshown in Equation 2.s=[s ₁ ,s ₂ , . . . ,s _(N) _(T) ]^(T)  [Equation 2]

Meanwhile, transmission powers can be set different from each other fortransmission informations s₁, s₂, . . . , s_(N) _(T) respectively. Ifthe transmission powers are set to P₁, P₂, . . . , P_(N) _(T) ,respectively, the transmission power adjusted transmission informationcan be represented as Equation 3.ŝ=[ŝ ₁ ,ŝ ₂ , . . . ,ŝ _(N) _(T) ]^(T)=[P ₁ s ₁ ,P ₂ s ₂ , . . . ,P _(N)_(T) s _(N) _(T) ]^(T)  [Equation 3]

And, Ŝ may be represented as Equation 4 using a diagonal matrix P of thetransmission power.

$\begin{matrix}{\overset{\hat{}}{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Let us consider a case of configuring N_(T) transmitted signals x₁, x₂,. . . , x_(N) _(T) , which are actually transmitted, by applying aweight matrix W to a transmission power adjusted information vector Ŝ.In this case, the weight matrix plays a role in properly distributingeach transmission information to each antenna according to atransmission channel status and the like. The transmitted signals areset to x₁, x₂, . . . , x_(N) _(T) may be represented as Equation 5 usinga vector X. In this case, W_(ij) means a weight between an i^(th)transmitting antenna and a j^(th) information. And, the W may be calleda weight matrix or a precoding matrix.

$\begin{matrix}{x = {\left\lbrack \begin{matrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{matrix} \right\rbrack = {{\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1N_{T}} \\w_{21} & w_{22} & \ldots & w_{2N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 1} & w_{i\; 2} & \ldots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \ldots & w_{N_{T}N_{T}}\end{bmatrix}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Generally, a physical meaning of a rank of a channel matrix may indicatea maximum number for carrying different informations on a grantedchannel. Since a rank of a channel matrix is defined as a minimum numberof the numbers of independent rows or columns, a rank of a channel isnot greater than the number of rows or columns. For example by equation,a rank of a channel H (i.e., rank (H)) is limited by Equation 6.rank(H)≤min(N _(T) ,N _(R))  [Equation 6]

Meanwhile, each different information sent by MIMO technology may bedefined as ‘transport stream’ or ‘stream’ simply. This ‘stream’ may becalled a layer. If so, the number of transport streams is unable to begreater than a channel rank, which is the maximum number for sendingdifferent informations. Hence, the channel matrix H may be representedas Equation 7.# of streams≤rank(H)≤min(N _(T) ,N _(R))  [Equation 7]

In this case, ‘# of streams’ may indicate the number of streams.Meanwhile, it should be noted that one stream is transmittable via atleast one antenna.

Various methods for making at least one stream correspond to severalantennas may exist. These methods may be described in accordance with atype of MIMO technique as follows. First of all, if one stream istransmitted via several antennas, it may be regarded as spatialdiversity. If several streams are transmitted via several antennas, itmay be regarded as spatial multiplexing. Of course, such an intermediatetype between spatial diversity and spatial multiplexing as a hybrid typeof spatial diversity and spatial multiplexing may be possible.

In the following description, an active antenna system (AAS) and a3-dimensional (3D) beamforming of one embodiment of the presentinvention are explained.

First of all, in an existing cellular system, a base station reducesinter-cell interference and enhances throughput (e.g., SINR (signal tointerference plus noise ratio)) of user equipments in a cell, using amechanical tilting or an electrical tilting. This is described in detailwith reference to the accompanying drawings as follows.

FIG. 4 is a diagram to describe an antenna tilting system.

Particularly, FIG. 4 (a) shows an antenna structure to which an antennatilting is not applied. FIG. 4 (b) shows an antenna structure to which amechanical tilting is applied. And, FIG. 4 (c) shows an antennastructure to which both a mechanical tilting and an electrical tiltingare applied.

Comparing FIG. 4 (a) and FIG. 4 (b) to each other, regarding amechanical tilting, as shown in FIG. 4 (b), it is disadvantageous inthat a beam direction is fixed in case of an initial installation.Moreover, regarding an electrical tilting, as shown in FIG. 4 (c),despite that a tilting angle is changeable using an internal phase shiftmodule, it is disadvantageous in that a very restrictive verticalbeamforming is available only due to a substantially cell-fixed tilting.

FIG. 5 is a diagram for one example of comparing an existing antennasystem and an active antenna system to each other.

Particularly, FIG. 5 (a) shows an existing antenna system, while FIG. 5(b) shows an active antenna system.

Referring to FIG. 5, in an active antenna system, unlike an existingantenna system, each of a plurality of antenna modules includes activedevices such as a power amplifier, an RF module and the like. Hence, theactive antenna system is capable of controlling/adjusting a power andphase for each of the antenna modules.

In a generally considered MIMO antenna structure, a linear antenna(i.e., 1-dimensional array antenna) like a ULA (uniform linear array)antenna is taken into consideration. In this 1-dimensional arraystructure, a beam generable by beamforming exists in a 2-dimensionalplane. This applies to a PAS (passive antenna system) based MIMOstructure of an existing base station. Although vertical antennas andhorizontal antennas exist in the PAS based base station, since thevertical antennas are combined into one RF module, beamforming invertical direction is impossible but the above-mentioned mechanicaltilting is applicable only.

Yet, as an antenna structure of a base station evolves into AAS, anindependent RF module is implemented for each antenna in a verticaldirection, whereby a beamforming in a vertical direction is possible aswell as in a horizontal direction. Such a beamforming is called anelevation beamforming.

According to the elevation beamforming, generable beams can berepresented in a 3-dimensional space in vertical and horizontaldirections. Hence, such a beamforming can be named a 3-dimensional (3D)beamforming. In particular, the 3D beamforming is possible because the1D array antenna structure is evolved into a 2D array antenna structurein a plane shape. In this case, the 3D beamforming is possible in a 3Darray structure of a ring shape as well as in a planar-shaped antennaarray structure. The 3D beamforming is characterized in that an MIMOprocess is performed in a 3D space owing to antenna deployments ofvarious types instead of an existing 1D array antenna structure.

FIG. 6 shows a general AAS Radio Architecture for implementing thepresent invention.

As shown in FIG. 6, AAS Radio Architecture may comprise a transceiverunit array, Radio Distribution Network (RDN) and antenna array.Transceiver unit array may comprise K TXU/RXU. So, K transmission orreception data units may be delivered to RDN, and the RDN may distributethese data unit to L antenna elements.

By using this architecture, the embodiments of the present invention canbe implemented.

Conventionally, eNB used antenna structure (e.g. Uniform Linear Array,Cross-polarized Array) for beamforming only on Azimuth direction. (e.g.3GPP LTE Release-8/9/10/11). However, the present invention is directedto 2D array structure for MIMO transmission scheme to improve the systemperformance.

FIGS. 7 and 8 show examples of 2D Array structure.

Specifically, FIG. 7 shows an M*N antenna array with each column of auniform linear array. And, FIG. 8 shows an M*N/2 antenna array with eachcolumn of a pair of cross-polarized arrays.

By using 2D Array Structure, as shown in FIGS. 11 and 12, beamforming onboth Azimuth angle (horizontal direction angle) and Elevation angle(vertical direction angle) can be possible. By using this, the followingfeatures can be implemented.

-   -   Sector specific elevation beamforming (e.g. Adaptive control        over the vertical pattern beam-width and/or downtilt)    -   Advanced sectorization in the vertical domain    -   User-specific elevation beamforming

Vertical Sectorization can improve system performance based on VerticalSector pattern gain. Also, Vertical Sectorization generally does notrequire additional standardization.

UE specific Elevation beamforming can improve SINR of UEs by determiningVertical antenna pattern to UE direction. But, contrary to VerticalSectorization or Sector-specific Vertical Beamforming, UE-specificelevation beamforming may require additional standardization. Forexample, 2 dimensional port structure requires UE's CSI estimation andfeedback mechanism for UE specific elevation beamforming.

DL MIMO enhancement elements for supporting UE specific elevationbeamforming may include:

-   -   UE CSI feedback enhancement (A. New codebook design; B. Schemes        for Codebook selection, update, change; C. CSI payload size)    -   CSI-RS change for UE specific elevation beamforming    -   Definition of antenna port for UE specific elevation beamforming    -   Downlink control enhancement for UE specific elevation        beamforming (Additional schemes to acquire common channel        coverage and/or RRM measurement reliability when the number of        antenna ports increases)

On the other hand, the followings are things to be considered whendesigning.

-   -   eNB antenna calibration errors (phase and time)    -   Estimation Errors    -   Downlink overhead    -   Complexity    -   Feedback overhead    -   Backward compatibility    -   Practical UE implementation    -   Reuse of existing feedback framework    -   Subband versus wideband feedback    -   Planar (or Rectangular) Array (Planar antenna architecture)

Following is the explanation for implementing the above scheme.

FIG. 9 is a diagram for defining elevation angle and horizontal angle.

As shown in the left side of FIG. 9, the Elevation angle can be definedfrom −90°˜90° with a reference to 0° on the horizontal plane. Also,horizontal angle can be defined from 0°˜180° as shown in the right sideof FIG. 9.

FIG. 10 shows an example of deployment of 2D array in 3D space.

As indicated in FIG. 10, the location of antenna element (n, m) hasdifference from each other. The space between neighboring antennas inhorizontal direction can be represented as d_(H) and the space betweenneighboring antenna in vertical direction can be represented as d_(V).

Besides the above mapping, the RDN can perform a complex weighting onthe signal from each port and distributes it among the sub-array, tocontrol of side lobe levels and tilting angle. The complex weightingincludes amplitude weighting and phase shift.

Let S_(p) be the set of the antenna elements in sub-array associatedwith antenna port p, then complex weights on antenna element (m, n) canbe given by:w _(m,n) =|w _(m,n)|exp(−j2πλ₀ ⁻¹(ϕ _(etilt) ·r _(m,n))),(m,n)∈S_(p)  [Equation 8]

where |W_(m,n)| is the amplitude weight on antenna element (m,n).

The element location vector r _(m,n) and unit directional vector ϕ_(etilt) can be respectively given by:r _(m,n)=[0 n·d _(H) m·d _(V)]^(T)ϕ_(etilt)==[cos θ_(etilt) cos φ_(escan) cos θ_(etilt) sin φ_(escan) sinθ_(etilt)]^(T)  [Equation 9]

θ_(etilt)—the vertical steering angle, and φ_(scan)—the horizontalsteering angle.

On the other hand, the radiation pattern for an antenna port p can begiven by:

$\begin{matrix}{{A_{p}\left( {\theta,\varphi} \right)} = {{A_{E}\left( {\theta,\varphi} \right)} + {10{\log_{10}\left( \left| {\sum\limits_{{({m,n})} \in S_{p}}{w_{m,n} \cdot v_{m,n}}} \right|^{2} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

where S_(p) is the set of antenna elements within the sub-arrayassociated with antenna port p, A_(E) (φ, θ) is the 3D element patterngiven in Table 1 of Appendix A, agreed in RAN4, φ the azimuth angle isdefined between −180° and 180°, and θ the elevation angle is definedbetween −90° and 90° (0° represents perpendicular to array).

ν_(m,n) the phase shift factor due to array placement is given by:ν_(m,n)=exp(j2πλ₀ ⁻¹(ϕ· r _(m,n))),(m,n)∈S _(p)ϕ=[cos θ cos φ cos θ sin φ sin θ]^(T)  [Equation 11]

It should be noted that the losses of the cable network should be addedto the max gain to calculate the gain of an active antenna, as given,for example, in Table 1 below.

TABLE 1 Horizontal radiation pattern${A_{E,H}(\varphi)} = {{- {\min\left\lbrack {{12\left( \frac{\varphi}{\varphi_{3{dB}}} \right)^{2}},A_{m}} \right\rbrack}}\mspace{14mu}{dB}}$Front to back ratio A_(m) = 30 dB Vertical radiation pattern${A_{E,V}(\theta)} = {- {\min\left\lbrack {{12\left( \frac{\theta}{\theta_{3{dB}}} \right)^{2}},{SLA}_{v}} \right\rbrack}}$Side lobe lower level SLA_(v) = 30 dB 3D element pattern A_(E) (φ, θ) =G_(E,max) − min{−[A_(E,H) (φ) + A_(E,V) (θ)], A_(m)} Additionalparameters are provided in A10 of Table 5.4.4.2.1-1 in TR37.840.

FIGS. 11-14 show application of 3D beam forming according to the presentinvention.

Specifically, as shown in FIG. 11, by using the present invention forbeamforming with Elevation angle, Sectorization on Vertical domain canbe available. At the same time, Horizontal Beamforming with Azimuthangle within the Vertical sector can be available.

And, as shown in FIG. 12, by using elevation beamforming, the basestation can support high quality service to users located in positionshigher than the antennas of the base station.

In urban area, there are buildings having various heights. Generally,the antenna of the base station is installed on the top of a specificbuilding, and the height of the buildings surrounding the specificbuilding can be higher or lower than the specific building.

FIG. 13 shows an example of a situation where antenna of the basestation is surrounded with high level buildings.

In this case, since there is no obstruction between the antenna of thebase station and the target, channel with strong LOS element can beestablished. Also, vertical beamforming to the high building may be moreimportant than the horizontal domain beamforming.

FIG. 14 shows an example of a situation where antenna of the basestation is located on the top of high level building and surrounded withlow level buildings.

In this case, a channel with lots of NLOS elements can be established,since the signals from the antenna of the base station can be refractedby the roof of the building and/or reflected by the floor of thebuilding. By using downward vertical beamforming, the various spacialchannels represented both by elevation angle and Azimuth angle can beestablished, espetially for the Users in the backside of a building.

Conventionally, codebook or feedback codebook for horizontal beamformingdivide Azimuth angle with equal interval (e.g., when designing DFT basedcodebook, 2*pi/N of exp(j*2*pi*n*k/N)⁰∥λ⁻|2*pi/N represents equalinterval division), or is designed to form a beam to arbitrary direction(e.g., precoding matrix with Random phase).

If the codebook for 3D beamforming divides Elevation angle domain andAzimuth angle domain with equal interval, the efficiency may be loweredsince there would be precoding matrixes not frequently used comparing toother precoding matrixes.

So, the following is for explaining the codebook design for implementingthe above 3D beam forming schemes.

To efficiently design the codebook for both horizontal directionbeamforming and vertical direction beamforming, one embodiment of thepresent invention proposed to design the codebook with a combination of2 types of precoding matrixes, one for horizontal direction and theother for the vertical direction. And, each of precoding matrix can beindicated with respective indicator or index (I₁, I₂).

FIG. 15 shows a concept of feedback the precoding matrix information inaccordance with the present embodiment of the invention.

UE may receive reference signals (RSs) from one or more eNBs (S1910).This RS can be CRS according to rel. 8 of LTE standard, or CSI-RSaccording to rel. 10 or later of LTE-A standard. When the UE receivesRSs, the UE may estimate the channel status and determine the preferredprecoding matrix both on horizontal direction and vertical direction.So, UE may select I₁ from the first type codebook for vertical beamforming and h from the second type codebook for horizontal beam forming.The indication of I₁ and I₂ can be changed.

Then, UE may report this precoding matrix information to the eNB (S1920,S1930). The I₁ and I₂ can be reported together, but they can be reportedat separate timing to reduce the reporting overhead. In one example, UEmay report I₁ with period P1 (S1920) and I₂ with period P2 (S1930). P1may be longer than P2.

When the eNB receives I₁ and I₂, eNB may construct the third typeprecoding matrix with the first type precoding matrix (Wv: precodingmatrix for vertical direction beam forming) and the second typeprecoding matrix (Wh: precoding matrix for horizontal direction beamforming). It should be noted that eNB may select Wv and Wh according toI₁ and I₂, and override these preferred precoding matrixes consideringthe situation of system. But, in the following explanation, we willassume that the Wv is selected based on I₁ and Wh is selected based onI₂. In any case, eNB selects Wv and Wh ‘considering’ I₁ and I₂.

In one example, eNB may select Wv and Wh with 1 to 1 correspondence asshown below.

TABLE 2 I I₁ ² 0 1 2 3 0 Wv(0), Wv(0), Wv(0), Wv(0), Wh(0) Wh(1) Wh(2)Wh(3) 1 Wv(1), Wv(1), Wv(1), Wv(1), Wh(0) Wh(1) Wh(2) Wh(3) 2 Wv(2),Wv(2), Wv(2), Wv(2), Wh(0) Wh(1) Wh(2) Wh(3) 3 Wv(3), Wv(3), Wv(3),Wv(3), Wh(0) Wh(1) Wh(2) Wh(3)

In another example, eNB may select two or more Wv based on I₁ and one ofthem is selected based on I₂. The same rational can be applied to theselection of Wh based on the combination of I₁ and I₂. This example canbe represented as Table 3 or 4 below.

TABLE 3 I₂ I₁ 0 1 2 3 4 5 6 7 0 Wv(0), Wv(0), Wv(0), Wv(0), Wv(1),Wv(1), Wv(1), Wv(1), Wh(0) Wh(1) Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3) 1Wv(1), Wv(1), Wv(1), Wv(1), Wv(2), Wv(2), Wv(2), Wv(2), Wh(0) Wh(1)Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3) 2 Wv(2), Wv(2), Wv(2), Wv(2), Wv(3),Wv(3), Wv(3), Wv(3), Wh(0) Wh(1) Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3) 3Wv(3), Wv(3), Wv(3), Wv(3), Wv(0), Wv(0), Wv(0), Wv(0), Wh(0) Wh(1)Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3)

TABLE 4 I₂ I₁ 0 1 2 3 4 5 6 7 0 Wv(0), Wv(0), Wv(0), Wv(0), Wv(1),Wv(1), Wv(1), Wv(1), Wh(0) Wh(1) Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3) 1Wv(2), Wv(2), Wv(2), Wv(2), Wv(3), Wv(3), Wv(3), Wv(3), Wh(0) Wh(1)Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3) 2 Wv(4), Wv(4), Wv(4), Wv(4), Wv(5),Wv(5), Wv(5), Wv(5), Wh(0) Wh(1) Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3) 3Wv(6), Wv(6), Wv(6), Wv(6), Wv(7), Wv(7), Wv(7), Wv(7), Wh(0) Wh(1)Wh(2) Wh(3) Wh(0) Wh(1) Wh(2) Wh(3)

In another example, eNB may use fixed Wv and Wh can be selected based onthe combination of I₁ and I₂. This example can be represented as Table5A below.

TABLE 5 I I₁ ² 0 1 2 3 0 Wv(0), Wv(0), Wv(0), Wv(0), Wh(0) Wh(1) Wh(2)Wh(3) 1 Wv(0), Wv(0), Wv(0), Wv(0), Wh(4) Wh(5) Wh(6) Wh(7) 2 Wv(1),Wv(1), Wv(1), Wv(1), Wh(0) Wh(1) Wh(2) Wh(3) 3 Wv(1), Wv(1), Wv(1),Wv(1), Wh(4) Wh(5) Wh(6) Wh(7)

In another example, the number of precoding matrix in the codebook forvertical direction varies depending on the index of the precoding matrixfor horizontal direction. The codebook for vertical direction maycomprise more precoding matrixes for 0°˜45° than the precoding matrixesfor 45°˜90° and 0°˜−90°. In another example, the codebook for verticaldirection may comprise more precoding matrixes for 0°˜45° than theprecoding matrixes for 0°˜90° and for −45°˜−90°.

Based on these selections, eNB may construct the precoding matrix for 3Dbeamforming. In one example, eNB may use Kronecker product of the twoprecoding matrixes (Wv and Wh).W _(l,m) =Wv _(l) ⊗Wh _(m)  [Equation 12]

By using this precoding matrix, eNB may transmit signals with 3Dbeamforming (S1940).

In another example, the UE may use two indicators for vertical directionprecoding matrix (V-I₁ and V-I₂). V-I₁ and V-I₂ can be reportedtogether, or separately. By using these two indicators, the precodingmatrix for vertical direction can be selected as Table 5B.

TABLE 5 V - I₂ V-I₁ 0 1 0 Wv (0) Wv (1) 1 Wv (1) Wv (2) 2 Wv (2) Wv (3)3 Wv (3) Wv (0)

In the following explanation, precoding matrix for vertical beamformingis assumed as Rank 1 precoding matrix, and precoding matrix forhorizontal beamforming is assumed as Rank M precoding matrix, where Mrepresents the number of transmission antennas. And, the precodingmatrix for horizontal beamforming can be used from among the followingprecoding matrix for 2D beamforming.

Codebook for transmission on antenna ports {0,1} and for CSI reportingbased on antenna ports {0,1} or {15,16} can be represented as:

TABLE 6 Codebook Number of layers υ index 1 2 0$\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\1\end{bmatrix}$ $\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}$ 1 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}$ 2 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 1 \\j & {- j}\end{bmatrix}$ 3 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\{- j}\end{bmatrix}$ —

On the other hand, the codebook for horizontal beamforming for Ranks 1and 2 may be selected from the following:

TABLE 7 i₂ i₁ 0 1 2 3 0-15 W_(i) ₁ _(,0) ⁽¹⁾ W_(i) ₁ _(,4) ⁽¹⁾ W_(i) ₁_(,8) ⁽¹⁾ W_(i) ₁ _(,12) ⁽¹⁾ i₂ i₁ 4 5 6 7 0-15 W_(i) ₁ _(+8,1) ⁽¹⁾W_(i) ₁ _(+8,5) ⁽¹⁾ W_(i) ₁ _(+8,9) ⁽¹⁾ W_(i) ₁ _(+8,13) ⁽¹⁾ i₂ i₁ 8 910 11 0-15 W_(i) ₁ ₊₁₆,₂ ⁽¹⁾ W_(i) ₁ _(+16,6) ⁽¹⁾ W_(i) ₁ _(+16,10) ⁽¹⁾W_(i) ₁ _(+16,14) ⁽¹⁾ i₂ i₁ 12 13 14 15 0-15 W_(i) ₁ _(+24,3) ⁽¹⁾ W_(i)₁ _(+24,7) ⁽¹⁾ W_(i) ₁ _(+24,11) ⁽¹⁾ W_(i) ₁ _(+24,15) ⁽¹⁾${{where}\mspace{14mu} W_{m,n}^{(1)}} = {\frac{1}{2}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}}\end{bmatrix}}$

TABLE 8 i₂ i₁ 0 1 2 3 0-15 W_(i) ₁ _(,i) ₁ _(,0) ⁽²⁾ W_(i) ₁ _(,i) ₁_(,4) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,4) ⁽²⁾ i₂i₁ 4 5 6 7 0-15 W_(i) ₁ _(+16,i) ₁ _(+16,0) ⁽²⁾ W_(i) ₁ _(+16,i) ₁_(+16,4) ⁽²⁾ W_(i) ₁ _(+24,i) ₁ _(+24,0) ⁽²⁾ W_(i) ₁ _(+24,i) ₁ _(+24,4)⁽²⁾ i₂ i₁ 8 9 10 11 0-15 W_(i) ₁ _(,i) ₁ _(+8,0) ⁽²⁾ W_(i) ₁ _(,i) ₁_(+8,4) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+16,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+16,4)⁽²⁾ i₂ i₁ 12 13 14 15 0-15 W_(i) ₁ _(,i) ₁ _(+24,0) ⁽²⁾ W_(i) ₁ _(,i) ₁_(+24,4) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+24,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+24,4)⁽²⁾${{where}\mspace{14mu} W_{m,m^{\prime},n}^{(2)}} = {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} & v_{m^{\prime}} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m^{\prime}}}\end{bmatrix}}$

Where:φ_(n) =e ^(j2πn/16)ν_(m)=[1e ^(j2πm/32)]^(T)

In another example, the codebook for horizontal beamforming for Ranks 1and 2 may be selected from the following:

TABLE 9 i₂ i₁ 0 1 2 3 0-15 W_(2i) ₁ _(,0) ⁽¹⁾ W_(2i) ₁ _(,1) ⁽¹⁾ W_(2i)₁ _(,2) ⁽¹⁾ W_(2i) ₁ _(,3) ⁽¹⁾ i₂ i₁ 4 5 6 7 0-15 W_(2i) ₁ _(+1,0) ⁽¹⁾W_(2i) ₁ _(+1,1) ⁽¹⁾ W_(2i) ₁ _(+1,2) ⁽¹⁾ W_(2i) ₁ _(+1,3) ⁽¹⁾ i₂ i₁ 8 910 11 0-15 W_(2i) ₁ _(+2,0) ⁽¹⁾ W_(2i) ₁ _(+2,1) ⁽¹⁾ W_(2i) ₁ _(+2,2)⁽¹⁾ W_(2i) ₁ _(+2,3) ⁽¹⁾ i₂ i₁ 12 13 14 15 0-15 W_(2i) ₁ _(+3,0) ⁽¹⁾W_(2i) ₁ _(+3,1) ⁽¹⁾ W_(2i) ₁ _(+3,2) ⁽¹⁾ W_(2i) ₁ _(+3,3) ⁽¹⁾${{where}\mspace{14mu} W_{m,n}^{(1)}} = {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}}\end{bmatrix}}$

TABLE 10 i₂ i₁ 0 1 2 3 0-15 W_(2i) ₁ _(,2i) ₁ _(,0) ⁽²⁾ W_(2i) ₁ _(,2i)₁ _(,1) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+1,0) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+1,1)⁽²⁾ i₂ i₁ 4 5 6 7 0-15 W_(2i) ₁ _(+2,2i) ₁ _(+2,0) ⁽²⁾ W_(2i) ₁ _(+2,2i)₁ _(+2,1) ⁽²⁾ W_(2i) ₁ _(+3,2i) ₁ _(+3,0) ⁽²⁾ W_(2i) ₁ _(+3,2i) ₁_(+3,1) ⁽²⁾ i₂ i₁ 8 9 10 11 0-15 W_(2i) ₁ _(,2i) ₁ _(+1,0) ⁽²⁾ W_(2i) ₁_(,2i) ₁ _(+1,1) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+2,0) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁_(+2,1) ⁽²⁾ i₂ i₁ 12 13 14 15 0-15 W_(2i) ₁ _(,2i) ₁ _(+3,0) ⁽²⁾ W_(2i)₁ _(,2i) ₁ _(+3,1) ⁽²⁾ W_(2i) ₁ _(+1,2i) ₁ _(+3,0) ⁽²⁾ W_(2i) ₁ _(+1,2i)₁ _(+3,1) ⁽²⁾${{where}\mspace{14mu} W_{m,m^{\prime},n}^{(2)}} = {\frac{1}{4}\begin{bmatrix}v_{m} & v_{m^{\prime}} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m^{\prime}}}\end{bmatrix}}$

TABLE 11 i₂ i₁ 0 1 2 0-3 W_(8i) ₁ _(,8i) ₁ _(,8i) ₁ ₊₈ ⁽³⁾ W_(8i) ₁_(+8,8i) ₁ _(,8i) ₁ ₊₈ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(,8i) ₁ _(+8,8i) ₁₊₈ ⁽³⁾ i₂ i₁ 3 4 5 0-3 {tilde over (W)}_(8i) ₁ _(+8,8i) ₁ _(,8i) ₁ ⁽³⁾W_(8i) ₁ _(+2,8i) ₁ _(+2,4i) ₁ ₊₁₀ ⁽³⁾ W_(8i) ₁ _(+10,8i) ₁ _(+2,8i) ₁₊₁₀ ⁽³⁾ i₂ i₁ 6 7 8 0-3 {tilde over (W)}_(8i) ₁ _(+2,8i) ₁ _(+10,8i) ₁₊₁₀ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+10,8i) ₁ _(+2,8i) ₁ ₊₂ ⁽³⁾ W_(8i) ₁_(+4,8i) ₁ _(+4,8i) ₁ ₊₁₂ ⁽³⁾ i₂ i₁ 9 10 11 0-3 W_(8i) ₁ _(+12,8i) ₁_(+4,8i) ₁ ₊₁₂ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+4,8i) ₁ _(+12,8i) ₁ ₊₁₂⁽³⁾ {tilde over (W)}_(8i) ₁ _(+12,8i) ₁ _(+4,8i) ₁ ₊₄ ⁽³⁾ i₂ i₁ 12 13 140-3 W_(8i) ₁ _(+6,8i) ₁ _(+6,8i) ₁ ₊₁₄ ⁽³⁾ W_(8i) ₁ _(+14,8i) ₁ _(+6,8i)₁ ₊₁₄ ⁽³⁾ {tilde over (W)}_(8i) ₁ _(+6,8i) ₁ _(+14,8i) ₁ ₊₁₄ ⁽³⁾ i₂ i₁15 0-3 {tilde over (W)}_(8i) ₁ _(+14,8i) ₁ _(+6,8i) ₁ ₊₆ ⁽³⁾$\quad\begin{matrix}{{{{where}\mspace{14mu} W_{m,m^{\prime},m^{''}}^{(3)}} = {\frac{1}{\sqrt{24}}\begin{bmatrix}v_{m} & v_{m^{\prime}} & v_{m^{''}} \\v_{m} & {- v_{m^{\prime}}} & {- v_{m^{''}}}\end{bmatrix}}},} \\{{\overset{\sim}{W}}_{m,m^{\prime},m^{''}}^{(3)} = {\frac{1}{\sqrt{24}}\begin{bmatrix}v_{m} & v_{m^{\prime}} & v_{m^{''}} \\v_{m} & v_{m^{\prime}} & {- v_{m^{''}}}\end{bmatrix}}}\end{matrix}$

TABLE 12 i₂ i₁ 0 1 2 0-3 W_(8i) ₁ _(,8i) ₁ _(+8,0) ⁽⁴⁾ W_(8i) ₁ _(,8i) ₁_(+8,1) ⁽⁴⁾ W_(8i) ₁ _(+2,8i) ₁ _(+10,0) ⁽⁴⁾ i₂ i₁ 3 4 5 0-3 W_(8i) ₁_(+2,8i) ₁ _(+10,1) ⁽⁴⁾ W_(8i) ₁ _(+4,8i) ₁ _(+12,0) ⁽⁴⁾ W_(8i) ₁_(+4,8i) ₁ _(+12,1) ⁽⁴⁾ i₂ i₁ 6 7 0-3 W_(8i) ₁ _(+6,8i) ₁ _(+14,0) ⁽⁴⁾W_(8i) ₁ _(+6,8i) ₁ _(+14,1) ⁽⁴⁾${{where}\mspace{14mu} W_{m,m^{\prime},n}^{(4)}} = {\frac{1}{\sqrt{32}}\begin{bmatrix}v_{m} & v_{m^{\prime}} & v_{m} & v_{m^{\prime}} \\{\varphi_{n}v_{m}} & {\varphi_{n}v_{m^{\prime}}} & {{- \varphi_{n}}v_{m}} & {{- \varphi_{n}}v_{m^{\prime}}}\end{bmatrix}}$

TABLE 13 i₂ i₁ 0 0-3$W_{i_{1}}^{(5)} = {\frac{1}{\sqrt{40}}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16}\end{bmatrix}}$

TABLE 14 i₂ i₁ 0 0-3$W_{i_{1}}^{(6)} = {\frac{1}{\sqrt{48}}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 16} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16} & {- v_{{2i_{1}} + 16}}\end{bmatrix}}$

TABLE 15 i₂ i₁ 0 0-3$W_{i_{1}}^{(7)} = {\frac{1}{\sqrt{56}}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 24} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16} & {- v_{{2i_{1}} + 16}} & v_{{2i_{1}} + 24}\end{bmatrix}}$

TABLE 16 i₂ i₁ 0 0 $W_{i_{1}}^{(8)} = {\frac{1}{8}\begin{bmatrix}v_{2i_{1}} & v_{2i_{1}} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 8} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 16} & v_{{2i_{1}} + 24} & v_{{2i_{1}} + 24} \\v_{2i_{1}} & {- v_{2i_{1}}} & v_{{2i_{1}} + 8} & {- v_{{2i_{1}} + 8}} & v_{{2i_{1}} + 16} & {- v_{{2i_{1}} + 16}} & v_{{2i_{1}} + 24} & {- v_{{2i_{1}} + 24}}\end{bmatrix}}$

Where:ϕ_(n) =e ^(jπn/2)ν_(m)=[1 e ^(j2πm/32) e ^(j4πm/32) e ^(j6πm/32)]^(T)

And, in this example, let's assume that the Rank 1 precoding matrix forvertical direction beamforming is selected as the same as the Rank 1precoding matrix for horizontal direction beamforming. Using thisassumption, following is an example of codebook for 3D beamforming.

Let's assume the 4 antenna ports case, where there are 2 antennas inhorizontal direction and 2 antennas in vertical direction.

Ranks 1 and 2 precoding matrixes are defined as:

$\begin{matrix}{W_{m}^{(1)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{m/4}}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{11mu} 13} \right\rbrack \\{W_{m}^{(2)} = {\frac{1}{2}\begin{bmatrix}1 & 1 \\e^{j2\pi{m/4}} & {- e^{j2\pi{m/4}}}\end{bmatrix}}} & \;\end{matrix}$

Horizontal direction precoding matrixes can be:Rank-1: Wh _(m) ⁽¹⁾ =W _(m) ⁽¹⁾Rank-2: Wh _(m) ⁽²⁾ =W _(m) ⁽²⁾

And, vertical direction precoding matrix can be:Wv _(l) ⁽¹⁾ =W _(l) ⁽¹⁾

then, the precoding matrix for 3D beamforming can be represented as:

$\begin{matrix}{\mspace{79mu}{{{Rank}\text{-}1\text{:}}{W_{l,m}^{(1)} = {{{{Wv}_{l}^{(1)} \otimes W}\; h_{m}^{(1)}} = {{{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{l/4}}\end{bmatrix}} \otimes {\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{m/4}}\end{bmatrix}}} = {\frac{1}{2}\begin{bmatrix}1 \\\begin{matrix}{e^{j\; 2\pi\;{l/4}}e^{j\; 2\pi\;{m/4}}} \\1 \\{e^{j\; 2\pi\;{l/4}}e^{j\; 2\pi\;{m/4}}}\end{matrix}\end{bmatrix}}}}}\mspace{20mu}{{Rank}\text{-}2\text{:}}\begin{matrix}{\mspace{79mu}{W_{l,m}^{(2)} = {{{Wv}_{l}^{(1)} \otimes W}\; h_{m}^{(2)}}}} \\{= {{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{l/4}}\end{bmatrix}} \otimes {\frac{1}{2}\begin{bmatrix}1 & 1 \\e^{j\; 2\pi\;{m/4}} & {- e^{j\; 2\pi\;{m/4}}}\end{bmatrix}}}} \\{= {\frac{1}{2\sqrt{2}}\begin{bmatrix}1 & 1 \\{e^{j\; 2\pi\;{l/4}}e^{j\; 2\pi\;{m/4}}} & {{- e^{j\; 2\pi\;{l/4}}}e^{j\; 2\pi\;{m/4}}} \\1 & 1 \\{e^{j\; 2\pi\;{l/4}}e^{j\; 2\pi\;{m/4}}} & {e^{j\; 2\pi\;{l/4}}e^{j\; 2\pi\;{m/4}}}\end{bmatrix}}}\end{matrix}}} & {\left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\mspace{14mu}}\end{matrix}$

In another example, a codebook for 8 antenna ports (4H+2V) can bedefined as following.

2 antenna ports

$\begin{matrix}{{{Rank}\text{-}1\text{:}}{W_{m}^{({1,{2{ports}}})} = {\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j2\pi{m/4}}\end{bmatrix}}}{{Rank}\text{-}2\text{:}}{W_{m}^{({2,{2ports}})} = {\frac{1}{2}\begin{bmatrix}1 & 1 \\e^{j\; 2\pi\;{m/4}} & {- e^{j2\pi{m/4}}}\end{bmatrix}}}} & \left\lbrack {{Equation}\mspace{14mu} 15} \right\rbrack\end{matrix}$

4 antenna ports

$\begin{matrix}{{\varphi_{n} = e^{j\; 2\pi\;{n/16}}}{v_{m} = \left\lbrack {1\mspace{14mu} e^{j\; 2\;\pi\;{m/32}}} \right\rbrack^{T}}{{Rank}\text{-}1\text{:}}{W_{m,n}^{({1,{4{ports}}})} = {\frac{1}{2}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}}\end{bmatrix}}}{{Rank}\text{-}2\text{:}}{W_{m,m^{\prime},n}^{({2,{4{por}ts}})} = {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} & v_{m} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}\nu_{m}}\end{bmatrix}}}} & \left\lbrack {{Equation}\mspace{14mu} 16} \right\rbrack\end{matrix}$

When 2 ports are defined for vertical domain, Rank 1 precoding matrixfor 2 ports can be:Rank-1: Wv _(l) ^((1,2 ports)) =W _(l) ^((1,2 ports))  [Equation 17]

When 4 ports are defined for horizontal domain, Ranks 1˜4 precodingmatrix for 4 ports can be:Rank-1: Wh _(m,n) ^((1,4 ports)) =W _(m,n) ^((1,4 ports))Rank-2: Wh _(m,m:n) ^((2,4 ports)) =W _(m,m:n) ^((2,4 ports))  [Equation18]

So, precoding matrix for 3D beamforming can be:

$\begin{matrix}{{{Rank}\text{-}1\text{:}}\begin{matrix}{W_{l,m,n}^{(1)} = {W{v_{l}^{({1,{2{ports}}})} \otimes W}h_{m,n}^{({1,{4{ports}}})}}} \\{= {{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j2\pi{l/4}}\end{bmatrix}} \otimes {\frac{1}{2}\begin{bmatrix}\nu_{m} \\{\phi_{n}\nu_{m}}\end{bmatrix}}}} \\{= {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}} \\{e^{j\; 2\pi\;{l/4}}\nu_{m}} \\{e^{j\; 2\pi\;{l/4}}\varphi_{n}v_{m}}\end{bmatrix}}}\end{matrix}{{{Rank}\text{-}2}:\begin{matrix}{W_{l,m,m^{\prime},n}^{(2)} = {W{v_{l}^{({1,{2{ports}}})} \otimes W}h_{m,m^{\prime},n}^{({2,{4{ports}}})}}} \\{= {{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j2\pi{l/4}}\end{bmatrix}} \otimes {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} & v_{m} \\{\varphi_{n}\nu_{m}} & {{- \varphi_{n}}v_{m}}\end{bmatrix}}}} \\{= {\frac{1}{4}\begin{bmatrix}v_{m} & v_{m} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m}} \\{e^{j\; 2\pi\;{l/4}}v_{m}} & {e^{j\; 2\;\pi\;{l/4}}v_{m}} \\{e^{j\; 2\pi\;{l/4}}\varphi_{n}v_{m}} & {{- e^{j2\pi{l/4}}}\varphi_{n}v_{m}}\end{bmatrix}}}\end{matrix}}} & \left\lbrack {{Equation}\mspace{14mu} 19} \right\rbrack\end{matrix}$

Following is an example for 16 antenna ports (=8(H)+2 (V)).

2 Antenna port

Rank-1: $W_{m}^{({1,{2{ports}}})} = {\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{m/4}}\end{bmatrix}}$ Rank-2:$W_{m}^{({2,{2{ports}}})} = {\frac{1}{2}\begin{bmatrix}1 & 1 \\e^{j\; 2\pi\;{m/4}} & {- e^{j\; 2\pi\;{m/4}}}\end{bmatrix}}$

8 Antenna port

φ_(n) = e^(j π n/2)v_(m) = [1  e^(j 2 π m/32)  e^(j4 π m/32)  e^(j 6 π m/32)]^(T)$W_{m,n}^{({1,{8{ports}}})} = {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}}\end{bmatrix}}$$W_{m,m^{\prime},n}^{({2,{8{por}ts}})} = {\frac{1}{4}\begin{bmatrix}v_{m} & v_{m} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m}}\end{bmatrix}}$

When 2 ports are defined on vertical domain, Rank 1 precoding matrix for2 ports can be:Rank-1: Wv _(l) ^((1,2 ports)) =W _(l) ^((1,2 ports))  [Equation 20]

When 4 ports are defined for horizontal domain, Ranks 1˜4 precodingmatrixes for 4 port can be:Rank-1: Wh _(m,n) ^((1,8 ports)) =W _(m,n) ^((1,8 ports))Rank-2: Wh _(m,m:n) ^((2,8 ports)) =W _(m,m:n) ^((2,8 ports))  [Equation21]

So, the precoding matrixes are 3D beamforming can be:

$\begin{matrix}{{{Rank}\text{-}1\text{:}}\begin{matrix}{W_{l,m,n}^{(1)} = {{{Wv}_{l}^{({1,{2\mspace{14mu}{ports}}})} \otimes W}\; h_{m,n}^{({1,{8\mspace{14mu}{ports}}})}}} \\{= {{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{l/4}}\end{bmatrix}} \otimes {\frac{1}{\sqrt{8}}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}}\end{bmatrix}}}} \\{= {\frac{1}{4}\begin{bmatrix}v_{m} \\{\varphi_{n}v_{m}} \\{e^{j\; 2\pi\;{l/4}}v_{m}} \\{e^{j\; 2\pi\;{l/4}}\varphi_{n}v_{m}}\end{bmatrix}}}\end{matrix}{{Rank}\text{-}2\text{:}}\begin{matrix}{W_{l,m,m^{\prime},n}^{(2)} = {{{Wv}_{l}^{({1,{2\mspace{14mu}{ports}}})} \otimes W}\; h_{m,m^{\prime},n}^{({2,{8\mspace{14mu}{ports}}})}}} \\{= {{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\; 2\pi\;{l/4}}\end{bmatrix}} \otimes {\frac{1}{4}\begin{bmatrix}v_{m} & v_{m} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m}}\end{bmatrix}}}} \\{= {\frac{1}{\sqrt{32}}\begin{bmatrix}v_{m} & v_{m} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m}} \\{e^{j\; 2\pi\;{l/4}}v_{m}} & {e^{j\; 2\;\pi\;{l/4}}v_{m}} \\{e^{j\; 2\pi\;{l/4}}\varphi_{n}v_{m}} & {{- e^{j2\pi{l/4}}}\varphi_{n}v_{m}}\end{bmatrix}}}\end{matrix}} & \left\lbrack {{Equation}\mspace{14mu} 22} \right\rbrack\end{matrix}$

Codebooks for the other number of antenna ports can be designed with thesame sequence.

FIG. 16 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 16 can be a user equipment WE) adapted toperform the above 3D beamforming operation, but it can be any apparatusfor performing the same operation.

As shown in FIG. 16, the apparatus may comprises a DSP/microprocessor(110) and RF module (transmiceiver; 135). The DSP/microprocessor (110)is electrically connected with the transciver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method for transmitting channel statusinformation (CSI) to a base station (BS) by a user equipment (UE) in awireless communication system, the method comprising: receivingreference signals (RSs) from the BS; and transmitting, to the BS, theCSI comprising a first codebook index for a first dimension and a secondcodebook index for a second dimension, based on the RSs, wherein thefirst codebook index represents a first precoding matrix comprising oneor more exponential functions dividing 2π by K and multiplying k,wherein k is within a range between 0 to K/2−1, wherein the secondcodebook index represents a second precoding matrix comprising one ormore exponential functions dividing 2π by H and multiplying h, wherein his within a range between 0 to H−1 to, and wherein K, k, H and h arenon-negative integers.
 2. The method of claim 1, wherein: K represents anumber of beams in the first dimension, and k represents a beam index inthe first dimension.
 3. The method of claim 1, wherein: H represents anumber of beams in the second dimension, and h represents a beam indexin the second dimension.
 4. The method of claim 1, wherein: the firstcodebook index is determined to form a beam within a half of a wholerange in the first dimension, and the second codebook index isdetermined to form a beam over a whole range in the second dimension. 5.The method of claim 1, wherein a 3D beam is defined by a kroneckerproduct between the first precoding matrix and the second precodingmatrix.
 6. A user equipment (UE) in a wireless communication system, theUE comprising: a transceiver; and a processor connected to thetransceiver and configured to: receive reference signals (RSs) from abase station (BS); and transmit, to the BS, channel status information(CSI) comprising a first codebook index for a first dimension and asecond codebook index for a second dimension, based on the RSs, whereinthe first codebook index represents a first precoding matrix comprisingone or more exponential functions dividing 2π by K and multiplying k,wherein k is within a range between 0 to K/2−1, wherein the secondcodebook index represents a second precoding matrix comprising one ormore exponential functions dividing 2π by H and multiplying h, wherein his within a range between 0 to H−1 to, and wherein K, k, H and h arenon-negative integers.
 7. The UE of claim 6, wherein: K represents anumber of beams in the first dimension, and k represents a beam index inthe first dimension.
 8. The UE of claim 6, wherein: H represents anumber of beams in the second dimension, and h represents a beam indexin the second dimension.
 9. The UE of claim 6, wherein: the firstcodebook index is determined to form a beam within a half of a wholerange in the first dimension, and the second codebook index isdetermined to form a beam over a whole range in the second dimension.10. The UE of claim 6, wherein a 3D beam is defined by a kroneckerproduct between the first precoding matrix and the second precodingmatrix.
 11. A method for receiving channel status information (CSI) froma user equipment (UE) by a base station (BS) in a wireless communicationsystem, the method comprising: transmitting reference signals (RSs) tothe UE; and receiving, from the UE, the CSI comprising a first codebookindex for a first dimension and a second codebook index for a seconddimension, based on the RSs, wherein the first codebook index representsa first precoding matrix comprising one or more exponential functionsdividing 2π by K and multiplying k, wherein k is within a range between0 to K/2−1, wherein the second codebook index represents a secondprecoding matrix comprising one or more exponential functions dividing2π by H and multiplying h, wherein h is within a range between 0 to H−1to, and wherein K, k, H and h are non-negative integers.
 12. The methodof claim 11, wherein: K represents a number of beams in the firstdimension, and k represents a beam index in the first dimension.
 13. Themethod of claim 11, wherein: H represents a number of beams in thesecond dimension, and h represents a beam index in the second dimension.14. The method of claim 11, wherein: the first codebook index isdetermined to form a beam within a half of a whole range in the firstdimension, and the second codebook index is determined to form a beamover a whole range in the second dimension.
 15. The method of claim 11,wherein a 3D beam is defined by a kronecker product between the firstprecoding matrix and the second precoding matrix.
 16. A base station(BS) in a wireless communication system, the BS comprising: atransceiver; and a processor connected to the transceiver and configuredto: transmit reference signals (RSs) to the UE; and receive, from theUE, the CSI comprising a first codebook index for a first dimension anda second codebook index for a second dimension, based on the RSs,wherein the first codebook index represents a first precoding matrixcomprising one or more exponential functions dividing 2π by K andmultiplying k, wherein k is within a range between 0 to K/2−1, whereinthe second codebook index represents a second precoding matrixcomprising one or more exponential functions dividing 2π by H andmultiplying h, wherein h is within a range between 0 to H−1 to, andwherein K, k, H and h are non-negative integers.
 17. The BS of claim 16,wherein: K represents a number of beams in the first dimension, and krepresents a beam index in the first dimension.
 18. The BS of claim 16,wherein: H represents a number of beams in the second dimension, and hrepresents a beam index in the second dimension.
 19. The BS of claim 16,wherein: the first codebook index is determined to form a beam within ahalf of a whole range in the first dimension, and the second codebookindex is determined to form a beam over a whole range in the seconddimension.
 20. The BS of claim 16, wherein a 3D beam is defined by akronecker product between the first precoding matrix and the secondprecoding matrix.